This invention relates to a herbicidal complex of 3-cyclohexyl-6-(dimethylamino)-1-methyl-s-triazine-2,4(1H,3H)-dione (hereinafter hexazinone) and urea in a molar ratio of 1:3.
3-Cyclohexyl-6-(dimethylamino)-1-methyl-s-triazine-2,4-(1H,3H)-dione (hereinafter hexazinone) is the active ingredient in Velpar.RTM. herbicide products manufactured by E. I. du Pont de Nemours & Co., Inc., Wilmington, Del. 19898. While Velpar.RTM. herbicide products can provide excellent control of a wide variety of weeds, brush and grasses at low application rates in industrial areas, i.e., rights-of-way, building foundations and the like, they are not generally suitable by themselves for agricultural uses.
It has been discovered that mixtures of hexazinone and 3-(3,4-dichlorophenyl)1,1-dimethylurea (hereinafter diuron) can provide good control of weeds and grasses in selected crops, particularly sugar cane. To avoid measuring errors, user exposure problems and delays which can occur when hexazinone and diuron formulations are tank mixed in the field just prior to use, it is often desirable that the two herbicides be formulated and sold as a mixture in a single package.
Field experience with hexazinone/diuron mixtures indicates that caking and agglomeration usually occur when the two herbicides are formulated as a wettable powder having more than about 60 percent by weight total active ingredients. The interaction of hexazinone and diuron appears to be a physical phenomenon which results in the formation of a eutectic composition which melts at about 60.degree. C. The presence of this relatively low melting point eutectic hexazinone/diuron mixture can cause significant problems in blending, grinding and screening operations required to prepare wettable powder formulations, and it presents a serious limitation on active ingredient concentration, which, from a commercial standpoint, preferably should be about 70 to 95 percent by weight.
It has now been discovered that hexazinone and urea form a complex in a molar ratio of 1:3 which, when formulated with the hexazinone/diuron mixture as a wettable powder, prevents the eutectic hexazinone/diuron composition from forming, and permits hexazinone/diuron mixtures having greater than 60 percent by weight total active ingredients which are free from caking and agglomeration.
The prior art teaches that certain di- and triazine compounds can form complexes with urea. Coll. Czech, Chem. Commun., 28, 2376 (1963) (C.A. 59, 10046h), for example, discloses a 1:1 molar complex of urea and 1 a (or b) which can be formed by aqueous crystallization: ##STR1## It is stated that urea adducts can be obtained from 5-azauracil (1a), 3-methyl-5-azauracil (1b), and 6-methyl-5-azauracil (1c). However, 1-methyl-5-azauracil and 4-methoxy-2-oxo-1,2-dihydro-1,3,5-triazine failed to form urea adducts. This would indicate that the hexazinone of this invention (2), i.e., ##STR2## would not form a complex or adduct with urea.
The J. Phys. Chem., 65, 1432 (1961) (Ca. A. 55, 24201i) discloses the formation of a 2:1 molar complex of urea with piperazine 3 when ##STR3## crystallized from an 8 molar aqueous urea solution.
Nippon Yakugakki Yakugaku Zasshi Tokyo, 75, 1029 (1955) (C.A. 50, 2121d) discloses that a 1:1 molar complex can be formed between urea and barbital 4, allobarbital 5, or ethylhexabital 6. ##STR4##
None of these references discloses a utility for any of the complexes which are taught.